The third case is directly related to aggression by part of one state or terrorist group towards another. NBC devices and poisonous substances are very attractive for terrorist pursuing agenda because the level of destruction that such weapons usually entail, and for states, such warheads imply not only a certain destruction capability, but a diplomatic - blackmailing - tool as well.

Thus, it should come to no one's surprise that there are individuals and organisations in hot pursue of such weapons, and despite contrary attempts, it is likely that we will see them for a long time to come.

Indeed, the level of destruction that natural or accidental releases could achieve is similar to that of a positive attack, but the long-term dangers and implications, in the last case, are much higher since by definition, accidents are casual and fairly unique, while attacks denote intentions, and while the sources of those attack survive, so does the threat.

Each one of these three kind of aggressive agents represents a slightly different scenario in terms of applicable countermeasures, albeit there are many similarities and procedures have been developed so as to make them simpler and homogeneous.

Nuclear devices are difficult to get, and despite their level of effectiveness in terms of destruction, biological and chemical weapons, thus, appear as more fashionable to crooks of all creeds and extreme political beliefs.

The problem with B and C class weapons is that they are more difficult to control in tactical terms, making them less usable in a state-against-state conflict, but since they are also cheaper, simpler to produce, and potentially more harmful than nuclear devices, they have their niche among ragtag dictatorships and terrorist organisations worldwide.